code: def test_symbolic_output_shape(self):
      from lasagne.layers.base import MergeLayer
  
      class WrongLayer(MergeLayer):
          def get_output_shape_for(self, input_shapes):
              return theano.tensor.vector().shape
  
      with pytest.raises(ValueError) as exc:
          WrongLayer([(None,)]).output_shape
      assert "symbolic output shape" in exc.value.args[0]
  
imports: from mock import Mock
  import numpy
  import pytest
  import theano
label_desc: Use image node_id 8 for calling the TestMergeLayer obj's underlying member method code with example usage: obj.test_symbolic_output_shape() and returns: theano